1. Field
Aspects of the present invention relates to an image forming apparatus such as a laser printer ,and a process cartridge which is detachably mountable to the image forming apparatus.
2. Description of the Related Art
As a process cartridge of a laser printer, there has been proposed a developing apparatus in which a toner unit accommodating a toner is detachably attached to a developing unit of the process cartridge.
In some developing apparatus, a toner box is detachably attached to the case of the developing apparatus. Slip-off prevention guide grooves are formed in the both right and left side walls of the case of the developing apparatus. A lever is pivotably disposed at the spindle that protrudes transversely from the both right and left sides of the toner box and rotates the rotary vane stirring the toner in the toner box, and an engaging projection is disposed at the substrate of the lever through which the spindle is inserted. In the developing apparatus, by simple operations of attaching the toner box to the case of the developing apparatus and pivoting the lever about the spindle to fit the engaging projection into the slip-off prevention guide groove, the lever and the toner box can be prevented from coming off from the case of the developing apparatus and the toner box is fixed to the developing apparatus.
In the developing apparatus, only one engaging projection is disposed at each of the left and right sides of the toner box, and only one slip-off prevention guide groove is disposed at each of the left and right side walls of the case of the developing apparatus. In other words, in the rotation direction of the rotary vane, the toner box is fixed to the developing apparatus at only one position where the engaging projection engages with the slip-off prevention guide groove.
When rotational moment is generated along with the rotation of the rotary vane, the fitting status of the engaging projection in the slip-off prevention guide groove may become unstable under the influence of the rotational moment. In this case, it becomes difficult to fix the toner box stably to the developing apparatus and a gap may be generateds between the toner box and the developing apparatus, which may cause a toner leakage.